The present invention is directed to a method for treating saturating papers used in decorative laminates, and more particularly, to a method for improving the absorption capacity of saturating papers.
Decorative laminates are widely used as decorative surfaces in a variety of structures such as counter tops, kitchen and bathroom work surfaces, wall panelings, floors, cabinets, partitions, doors, coverings for furniture, and the like. A typical decorative laminate includes three separate layers: 1) a core, 2) a decorative sheet located over the core, and 3) an overlay sheet located on top of the decorative sheet. The core is typically made of a plurality of kraft paper sheets that are impregnated with a thermosetting resin. The decorative sheet, also known as the decor sheet, is typically made of a fibrous sheet. The decor sheet provides the visible surface of the finished decorative laminate and may, for example, have a printed design (such as a wood grain) or a coloring agent dispersed throughout the decor sheet. The overlay sheet is located over the decor sheet and can be made of a high quality alpha cellulose paper. The overlay sheet provides a protective layer to the decorative laminate. The core sheets, decor sheet, and overlay sheets that make up the decorative laminate are each known as a type of xe2x80x9csaturating paperxe2x80x9d.
In order to form the decorative laminate, a number of core sheets are bonded together to form a core, and the decor sheets are located on top of the core. An overlay sheet is then typically immersed in a resin, such as a melamine-formaldehyde saturating resin, such that the overlay sheet absorbs a portion of the resin. The overlay sheet is then removed from the resin bath and the resin in the overlay sheet is allowed to at least partially dry to improve the handling characteristics of the overlay sheet. The partially-dried overlay sheet is then located on the decor sheet, and heat and pressure are applied to the laminate to bond the overlay sheet to the underlying decor sheet and core sheets. The decorative laminate is then further processed to form the finished decorative laminate product.
When the overlay sheets are immersed in the resin bath, it is desired that the overlay sheets absorb relatively large amounts of the resin. The more resin the overlay sheets absorb, the more the pre-impregnation basis weight of the overlay sheets can be reduced. Reducing the weight of the overlay sheets helps to lower the overall weight of the finished decorative laminate product.
Overlay sheets are typically xe2x80x9crefinedxe2x80x9d during their manufacture. The overlay sheets are made from a paper slurry, and the refining process includes passing the paper slurry between a pair of plates to fibrillate the pulp fibers. The refining process increases the surface area of, and reduces the length of, the fibers in the pulp, which increases the strength and uniformity of the overlay sheets. However, the refining process decreases the absorption capacity of the resultant overlay sheets. Thus, prior art methods for increasing the absorption capacity of the overlay sheet have largely concentrated on reducing the refining of the overlay sheets during the formation of the overlay sheet. However, the reduction of the refining of the overlay sheets compromises the strength and uniformity of the overlay sheet. Accordingly, there is a need for a method for increasing the absorption capacity of overlay sheets without compromising the strength and/or uniformity of the overlay sheets.
The present invention is a method for increasing the absorption capacity of saturating papers, such as overlay sheets, without substantially decreasing the strength or uniformity of the saturating paper. The method of the present invention includes embossing the saturating papers before they are soaked with resin. The embossing process increases the absorption capacity of the saturating papers, and does not require that the refining of the saturating papers be reduced. Another advantage of the method of the present invention is that the method is practiced after the saturating papers are dried and formed (i.e. the sheets are not in their slurry form), which enables easier processing of the sheets during the absorption-increasing process.
In a one embodiment, the present invention is a method for forming a saturating paper comprising the steps of selecting a sheet of paper, creating an embossed pattern of polygons or other geometric shapes on the sheet to increase the absorption capacity of the sheet, and causing a resin to contact the sheet such that the sheet absorbs at least a portion of the resin. The invention also includes a method for forming a decorative laminate including the steps of providing an overlay sheet, embossing the overlay sheet to increase the absorption capacity of the overlay sheet, and causing a resin to contact the overlay sheet such that the overlay sheet absorbs at least a portion of the resin. The method also includes the steps of locating the overlay sheet onto a decor sheet, and heating the overlay sheet and the decor sheet under pressure to bond the overlay sheet to the decor sheet.
Other objects and advantages of the present invention will be apparent from the following description and the accompanying drawings.